INTRODUCTION. 7 



Kearney, and Professor A. O. Garret t have all sent specimens from Utah; Profes- 

 sor T. D. A. Cockerell and Mr. Merritt Gary have sent specimens from Colorado; 

 Dr. P. A. Rydberg has brought many specimens from the Rocky Mountain region; 

 Messrs. Paul C. Standley, E. O. Wooton, Vernon Bailey, and H. L. Shantz have 

 sent specimens from the southwestern United States; Brother Leon, of the Colegio 

 de la vSalle, Havana, and Dr. Juan T. Roig, of the Estacion Agronomica, Santiago 

 de las Vegas, Cuba, have contributed Cuban specimens, and Dr. J. A. Shafer has 

 collected widely in Cuba; Mr. William Harris, of Hope Gardens, Jamaica, has col- 

 lected for us in Jamaica; Dr. John K. Small has obtained collections from nearly 

 all over the southeastern United States, aided by Mr. Charles Deering. Dr. Henry 

 H. Rusby and Dr. Francis W. Pennell have contributed plants and specimens from 

 Colombia, collected in 1917 and 1918. Mr. Frederick V. Coville, of the United 

 States Department of Agriculture, has made many valuable suggestions during the 

 progress of the investigation. 



In our studies we have also had use of the cacti of the following American 

 collections: Herbarium of the Missouri Botanical Garden at St. Louis; the Gray 

 Herbarium of Harvard University; the Rocky Mountain Herbarium at Laramie, 

 Wyoming; the collection of the United States Department of Agriculture; the 

 herbarium of the University of California, especially the Brandegee collection; and 

 the herbarium of the Field Museum of Natural History. 



The types of the new species described in this work are deposited in the herbaria 

 of the New York Botanical Garden and the United States National Museum, unless 

 otherwise indicated. 



In greenhouse collections many kinds of cacti grow very slowly, and flower 

 only after many years' cultivation. We have a number of plants of this kind 

 from various parts of America. It is hoped that some of them may bloom during 

 the period of publication of this book and thus enable us to include them in an 

 appendix. 



Fio. i. Percskia pereskia. Grown as a hedge. 



